The present invention relates to torque-applying and measuring apparatus, such as torque wrenches and, in particular, to electronic torque wrenches of the type which can display the applied torque level and/or a predetermined alarm torque level.
One standard type of torque wrench utilizes two beams which are interconnected at one end, but not at the other. One beam is rigid and the other is flexible in response to applied torque so as to produce relative movement with respect to the adjacent end of the rigid or inflexible beam, which movement is measured by an appropriate scale. This type of torque wrench is capable of measuring and indicating the actual value of torque being applied. Electronic versions of such wrenches typically utilize a strain gauge bending beam, the strain gauges being arranged with associated circuitry to cancel the effects of hand-hold position on the wrench handle.
Another type of torque wrench is the "click" type, in which the two beams are both rigid, and their free ends are coupled together by an adjustable spring-biased mechanism designed to yield and allow one of the beams to pivot relative to the other when a predetermined torque corresponding to the adjustable spring bias is reached. This pivoting movement typically produces a tactile vibration and an associated audible sound or "click" to signify that the predetermined torque level has been reached. This type of wrench is affected by hand-hold position errors.
In the bending-beam type of torque wrench, if a ratchet head is to be used it must be attached between the bending beam drive and the work, thus undesirably extending the drive configuration below the wrench body. Alternatively, a ratchet head can be attached in front of the bending beam drive necessitating an adjustment in reading to compensate for the "effective length" of the wrench configuration. This configuration is also subject to reading inaccuracies due to hand-hold position.
Similarly, the prior "click"-type torque wrench must typically be enlarged to accommodate a ratchet drive head and would necessarily add thickness or extension to the wrench body.
A prior "click"-type torque wrench provided by Consolidated Devices Inc. under Model No. 20005MF utilizes a pivoting beam which pivots about the torquing axis of the head, thereby eliminating hand-hold position errors. But this is a mechanical wrench and has the disadvantage of other "click"-type torque wrenches in that it cannot measure actual torque applied, but can only detect when a predetermined torque level is reached.